Application of Highway Safety Manual

The impact of predictive safety assessment based on quantitative methodology of the Highway Safety Manual (HSM) is significant particularly in urban roadway facilities. The responsibilities of safety professionals, transportation planners, and decision makers are critical for safe and efficient transportation in the ever-increasing travel demand in urban areas. The purpose of this study was to develop a Prediction Safety Assessment Tool (PSAT) of converting one urban roadway facility type to another with the application of predictive methodology and principles in the HSM. This tool is intended to help safety professionals, transportation planners, and decision-makers to evaluate safety effects considering the local conditions to make informed decisions in the planning process from the perspective of traffic safety. This study focuses on developing a proof-of-concept framework of this safety assessment tool for converting one facility to another with improvements to specific geometric elements in urban settings. By considering the traffic exposure, existing geometric conditions, and unit length of corridor (i.e., 1-mile of corridor length), this tool (excel spreadsheet) enables the safety analysts to evaluate existing and proposed facilities. This tool covers a wide range of urban roadway segments including 2-lane undivided roadway; 2-lane with two-way left-turn lane roadway; 4-lane undivided and 4-lane divided roadway; 4-lane undivided roadway with two-way left-turn lane, 6-lane undivided lane and 6-lane divided roadway; 6-lane undivided roadway with two-left turn lane, and 8-lane divided roadway. This excel spreadsheet was developed with customization to help the safety analysts input values in color-coded area with recommend range from the HSM. The output of the crash prediction and sensitivity analysis (i.e., the impact of traffic volume on predicted crashes in comparison facilities of interest) were graphically displayed. Thus, this tool displays user-friendly dashboard for the safety analysts with a conversion factor as well the predicted crash frequency, the distributions of collision types (i.e., single- and multi-vehicle collisions) by injury severity levels and impact of traffic volume as part of sensitivity analysis based on well-researched HSM methodology.